The present invention relates to a polarizing converter, and a method of manufacturing the same, which increases and extracts luminous light with a specific plane of polarization by rotating and adding luminous flux having a different plane of polarization, when luminous flux with a large component of the specific plane of polarization is extracted by the incident of natural light with a plurality of planes of polarization at the polarizing converter. The present invention further relates to an optical transducer using the polarizing apparatus, and an electronic device using this optical transducer.
As one example of an optical transducer using the polarization of light may be cited a liquid crystal display device. As such a device is known, for example, the backlit liquid crystal display device 300 shown in FIG. 23. In this liquid crystal display device 300, on the side from which light from a backlight 310 is impinged on a liquid crystal cell 320, a polarizer 330 is disposed before the liquid crystal cell 320, and light passing through the liquid crystal cell 320 is passed through an analyzer 340.
Light emitted from the backlight 310 has planes of polarization in all directions, but this light can be thought of as including, for example, luminous flux having a vector component in the vertical direction and luminous flux having a vector component in the horizontal direction orthogonal to the vertical direction. In optical terms the former could be referred to as the p-polarized light and the latter as the s-polarized light.
The polarizer 330 is an absorbing or reflecting type which for example allows the component of luminous flux in the vertical plane to pass, while not allowing the component of luminous flux in the horizontal plane to pass. In a liquid crystal display device, the absorbing type is normally used. In a normally-white liquid crystal display device, the polarizing plane of light passed through the analyzer 340 lets the light passed through the polarizer 330 coincide with the plane of polarization rotated through the given twist angle of the liquid crystal cell 320.
For natural light, the vector components in the vertical and horizontal polarizing planes are each 50%. Therefore, in principle 50% of the light is lost when the light is passed through the polarizer 330. In practice, taking the incident light as 100%, because of other losses the light passed by the polarizer 330 is not more than 35%.
In a reflective liquid crystal display device, the light-transmitting performance of the polarizer disposed on the side of the incident light is similar to that of the above backlit type of liquid crystal display device.
Thus, in a conventional liquid crystal display device 300 using the polarizer 330, only a portion of the incident light can be used for display, and this is an obstacle to the reduction of power consumption and the increase of luminosity of liquid crystal display devices.
For example, in a backlit type of liquid crystal display device 300, since the use efficiency of the light at the polarizer 330 is low, a light source capable of providing at least twice the amount of light that can be transmitted by the polarizer 330 is required. For this reason, conventionally, in for example a notebook computer provided with a liquid crystal display device, a large proportion of the required power supply is consumed by the backlighting light source. As a result, unless the power for the backlighting can be reduced, there is a limit to the degree to which the power consumption of the liquid crystal display device can be reduced.
Moreover, since the light from the backlighting is absorbed by the polarizer (polarizing plate), and is converted to heat, the panel surface becomes hotter, exerting a deleterious influence on the elements of the panel, the chemical structure of the liquid crystal, and so forth. Thus, it reduces the optical performance and the reliability of the liquid crystal display device.
The object of the present invention, considering these problems with the prior art, is to provide a polarizing apparatus which significantly eliminates the losses occurring when aligning the direction of polarization of incident light, and allows the optical efficiency to be improved.
Another object of the present invention is the provision of a method of fabricating the polarizing apparatus which can be applied to the manufacture of a polarizing apparatus of the above description.
A further object of the present invention is to construct an optical transducer such as a liquid crystal display device using the above polarizing apparatus, so as to provide an optical transducer such that the optical efficiency can be improved, and a brighter display screen can be achieved, or a substantial reduction in the power consumption of the light source can be attained.
Yet another object of the present invention is to construct an electronic device using the above optical to transducer, so as to provide an electronic device in which the optical efficiency can be improved, and a brighter display screen is achieved, or the power consumption of the light source can be substantially reduced, whereby further as a result of the improved optical efficiency the functional reliability can be improved and the device can be made more compact.
According to one aspect of the present invention, a polarizing apparatus for polarizing incident light having planes of polarization to light having a particular plane of polarization, comprising:
an optically active material disposed so as to exhibit anisotropy with respect to the optical activity; and
wherein the optically active material increases the intensity of luminous flux having the particular plane of polarization and reduces the intensity of luminous flux having a plane of polarization perpendicular to the particular plane of polarization.
The property of optical activity exhibited by the optically active material used in the present invention refers to the phenomenon whereby when plane polarized light passes through a material, the emitted light has a plane of polarization rotated through a particular angle with respect to the incident light. The material exhibits such phenomenon referred to optically active material.
Optically active materials can be broadly divided into two classes: those which exhibit optical activity in a crystalline structure in which the molecules have no chiral center, and organic substances possessing a chiral center such as an asymmetric carbon atom within the molecule. Examples of the former include quartz, cinnabar, lithium-potassium sulfate, LiKSO4, sodium perchlorate and sodium bromate. Examples of the latter include lactic acid, tartaric acid, tartrates, sucrose, alanine, grape sugar, ard glucose.
Taking as an example the case of an organic substance in which the molecules include a chiral center, for a single molecule, as shown in FIG. 1, a first incident vector component 10 of incident light in a certain plane of polarization, being for example the horizontal plane of polarization as shown in FIG. 1, is rotated within the optically active material 1 through an angle xcex81 with respect to the horizontal plane of polarization. Meanwhile a second incident vector component 20 of incident light in the other plane of polarization, being for example the vertical plane of polarization as shown in FIG. 1, is rotated within the optically active material 1 through an angle xcex82 with respect to the vertical plane of polarization. The relative magnitudes of the optical rotation angles are for example such that xcex81 less than xcex82. Thus viewing a single molecule it exhibits anisotropy of optically activity.
However, with a large number of molecules in a solid in the amorphous state, in a polymer, or in an aqueous solution, the anisotropy of each individual molecule is unordered, and mutually canceled out ever the number of molecules, so that the optical rotation angle becomes the same in all orientations and the anisotropy is lost.
In the present invention, it is possible to use an optically active material disposed so as to exhibit anisotropy of optically activity. For this purpose, the optically active material comprises optically active molecules, and three-dimensional orientations of the optically active molecules are aligned in order to produce the anisotropy with respect to the optical activity even in the bulk.
As shown in FIG. 1, a first incident vector component 10 of incident light having the horizontal plane of polarization, is rotated through an angle xcex81 to become a first emitted vector component 12. Meanwhile a second incident vector component 20 of incident light having the vertical plane of polarization is rotated through an angle xcex82, to become a second emitted vector component 22. At this time the optically active material is disposed so as to exhibit anisotropy such that xcex81 less than xcex82.
The first emitted vector component 12 after rotation can be split into a first horizontal vector component 12a and a first vertical vector component 12b. Similarly the second emitted vector component 22 after rotation can be split into a second horizontal vector component 22a and a second vertical vector component 22b. 
When compared with the original first incident vector component 10, the transmitted first horizontal vector component 12a is hardly reduced from the horizontal vector component thereof, and the transmitted first vertical vector component 12b is slightly increased. On the other hand, when compared with the original second incident vector component 20, the transmitted vertical vector component 22b is considerably reduced, and the transmitted second horizontal vector component 22a is increased.
Therefore, the total horizontal vector component of the emitted light is larger than the total vertical vector component.
Thus, by impinging the light on an optically active material with anisotropy, it will be seen than polarizing conversion such as to increase the amount of light having a particular plane of polarization occurs.
Each of the molecules may comprise for example a rigid molecule portion, a chiral center joined thereto, and at least one substituent joined to the chiral center, wherein the direction from the rigid molecule portions to the chiral centers are substantially aligned in the same direction, and the three-dimensional orientations of the substituents seen from the chiral centers are aligned in substantially the same direction. By this means, the above described anisotropy of optical activity is ensured.
The optically active material may be formed with a polymer. In this case, the three-dimensional orientations of the optically active molecules are substantially aligned by stretch-orientation of the polymer. By this means, the anisotropy of optical activity can be ensured.
The optically active material may have a given thickness in the passing direction of the light necessary for polarizing conversion, and may be divided into a plurality of layers in the direction of the given thickness. The three-dimensional orientations of the optically active molecules in each layer may be differently aligned for each layer, so as to increase the intensity of light flux having the particular plane of polarization. At this time, with regard to the mutual positioning of the layers, it is preferable for the layers to have the three-dimensional orientations of the optically active molecules constituting each layer and aligned differently, so as to increase the intensity of light flux having the particular plane of polarization to a maximum. Specifically, a subsequent layer should be oriented so that the component with the plane of polarization of maximum magnitude obtained from a previous layer can be further increased.
That is to say, the layers may be constituted by polarizing layers formed of the optically active material laminated in the direction of passage of light. In this way, each layer increases for example the horizontal component in FIG. 1 and reduces the vertical component, and it is possible for the amount of light having a particular plane of polarization to be further increased. At this time, with regard to the mutual positioning of the layers, it is preferable for the layers to have the three-dimensional orientations of the optically active molecules constituting each polarizing layer, and aligned differently so as to increase the intensity of luminous flux having the particular plane of polarization to a maximum.
Even further, the optically active material may be constituted by an anisotropic crystalline structure having a thickness in the direction of passage of the incident light, in order to amplify light having the particular plane of polarization is amplified and to reduce light having a plane of polarization perpendicular to the particular plane of polarization, when the incident light passes through the optically active material.
The optically active material may further include a combined base polymer.
In this case, compared with the case in which the optically active material alone is used, the fabrication of the polarizing apparatus is made easier.
The optically active material may be combined in a state of solution in the base polymer.
The base polymer used in this case may be a water-soluble base polymer comprising at least one of polyvinyl alcohol, polyvinyl pyrollidone, and polyamino acid; and
wherein the optically active material is a water-soluble optically active material comprising at least one of tartaric acid, lactic acid, tartrates, sugars, amino acids, and their derivatives.
As other combinations, the base polymer may be an organic solvent-soluble polymer comprising at lest one of polyvinyl acetate, polymethyl methacrylate, polyethyl methacrylate, epoxy resin, alkyd resin, urea resin, nitrocellulose, cellulose acetate, polyethylene terephthalate, nylon, phenol resin, phenol/resol resin, polyvinyl chloride, polyvinylidene chloride, vinyl chloride and vinyl acetate copolymer, and polystyrene and styrene/acrylonitrile copolymer; and
wherein the optically active material is an organic solvent-soluble optically active material comprising at least one of chiral smectic C phase and I phase liquid crystals, liquid crystal composites, and amino acid esters.
In the present invention, crystals of the optically active material having anisotropy with respect to optical activity may be dispersed in combination with the base polymer.
In this case, as combinations the base polymer may be a water-soluble base polymer comprising at least one of polyvinyl alcohol, polyvinyl pyrollidone, and polyamino acid; and
wherein the optically active material is a water-insoluble optically active material comprising at least one of chiral smectic C phase and I phase liquid crystal, quartz, and cinnabar crystals.
As other combinations, the base polymer may be an organic solvent-soluble polymer comprising at lest one of polyvinyl acetate, polymethyl methacrylate, polyethyl methacrylate, epoxy resin, alkyd resin, urea resin, nitrocellulose, cellulose acetate, polyethylene terephthalate, nylon, phenol resin, phenol/resol resin, polyvinyl chloride, polyvinylidene chloride, vinyl chloride and vinyl acetate copolymer, and polystyrene and styrene/acrylonitrile copolymer; and
wherein the optically active material is an organic solvent-insoluble optically active material comprising at least one of quartz, cinnabar, lithium-potassium sulfate, sodium perchlorate or sodium bromate, sugars and their derivatives, or glycoprotein crystals.
The optically active material includes a substance possessing the following formula: 
The optically active material includes a substance possessing the following formula: 
The optically active materials having the above two formulas may have the principal linking direction of the rigid molecular portion from the C8H17 to the asymmetric carbon atom of the optically active molecules aligned in substantially the same direction, and the three-dimensional orientation of the substituents CH2, C2H5, and H are substantially equal.
Furthermore, the base polymer preferably has combined therewith an optically active material being formed of water-soluble macromolecules, and having as a constituent substance at least one of polyamino acids, main chain or side chain macromolecular liquid crystals, polysaccharides, glycoproteins, and their derivatives. Alternatively, the base polymer preferably has combined therewith an optically active material being formed of organic solvent-soluble macromolecules, and having a polyester type macromolecular liquid crystal in which the monomer element has a chiral center.
If the base polymer exhibits optical activity, then optical rotation can also be carried out by optical activity of the optically active material itself combined with the base polymer, and a larger optical rotation can be applied to the incident light.
In this case it is preferable that the base polymer has to wavelength distribution characteristics which compensate for the wavelength distribution characteristics with respect to optical activity of the optically active material combined with the base polymer.
By this means, uniform wavelength distribution characteristics can be obtained for the polarizing apparatus, and the situation in which the light emitted from the polarizing apparatus is tinged with a color can be avoided.
Further, the optically active material other than the base polymer may comprise various kinds of optically active materials, and one of the optically active materials exhibits waveform distribution characteristics which compensate the waveform distribution characteristics with respect to optical activity in the visible light spectrum of another optically active material.
In this case again, uniform wavelength distribution characteristics can be obtained for the polarizing apparatus.
In the present invention, a liquid may be used as the optically active material.
In this case, the polarizing apparatus may have an optically active material including a fluid sugar solution exhibiting optical activity is sandwiched between two transparent plates each of which having a surface provided with an oriented film facing another oriented film. By making the angle between the two oriented films correspond to the angle through which the light is finally to be rotated, the amount of light of the particular plane of polarization can be increased to the maximum.
Alternatively, between two transparent plates having surfaces provided with transparent electrodes, the polarizing apparatus may have sandwiched an optically active material including a ferroelectric liquid crystal having fluidity and exhibiting optical activity, and adapted so that a voltage can be applied between electrodes of the two transparent plates.
Since the ferroelectric liquid crystal which is the optically active material exhibits orientation in response to an electric field, it can be oriented in a specific direction by application of a voltage, and the amount of light of the particular plane of polarization can be increased to the maximum.
As one application of the above-mentioned polarizing apparatus, the polarizing apparatus can be disposed as a preliminary stage before a polarizer of an optical transducer, or alternatively it can be used as the polarizer itself.
This polarizing apparatus amplifies light having a particular plane of polarization to have greater quantity than the incident light, and can pass this light through a polarizer to the liquid crystal cell, or directly to the liquid crystal cell. As a result, light of a different plane of polarization which would in a conventional polarizing device have been absorbed by the polarizer can be used as light for the display, and the liquid crystal display can be made brighter.
Further, in an optical transducer (such as a liquid crystal display device) using a backlight as a light source, even with a reduced power rating for the light source the same brightness can be obtained, so that the large amount of power for the light source consumed for the liquid crystal display can be reduced, and the device can be made more compact.
The optical transducer may have a lamp unit provided as a light source, and the polarizing apparatus may be disposed immediately adjacent to the output side of the lamp unit. In this way, the required number of polarizing apparatus is to reduced, and the optical design can be simplified, among other benefits.
Furthermore the optical transducer may comprise a liquid crystal cell which is either a transmitting or a reflecting type.
Further again, by provision of the above described optical transducer, an electronic device may be constituted, having a display screen formed for display of information depending on the state of liquid crystal molecules of the liquid crystal cell.
This electronic device may be a liquid crystal projector, or it may be a personal computer with multimedia support, or an engineering workstation (EWS), or it may further be a pager, a portable telephone, a word processor, a television, a video recorder of the viewfinder type or of the directly viewed monitor type, a digital still camera, an electronic notebook, an electronic calculator, a car navigation device, a point-of-sale terminal, or a device equipped with a touch panel.
Yet further by way of example, such an electronic device may be beeper, a hand-held terminal, a watch, or the like. Moreover, this is not restricted to a device using liquid crystals, as in a liquid crystal display device, but may be applied to any optical element using a polarization effect, such as an element having an electrooptic effect which rotates a particular plane of polarization by the application of a voltage, or an optical switch using the same.
The method of the present invention is a method of manufacturing a polarizing apparatus for polarizing incident light into light having a particular plane of polarization comprising:
a combining step for combining a base polymer and an optically active material;
a casting step for pouring the combined solution into a film;
a drying step for drying and hardening the solution formed into a film; and
a stretching step for applying tension to and stretching the hardened film.
In the method of the present invention, in the casting step in which the combined solution of base polymer and optically active material is poured into a film, the molecules of the optically active material are naturally aligned in the direction of least resistance. Then in the stretching step after drying, the optically active molecules which have been to a certain degree aligned in the casting step, have their orientation further oriented by the stretching step. In this way, the anisotropy of optical activity is obtained.
In this method, in the casting step it is preferable that the combined solution is poured along at least one groove. This is because the molecules tend to be aligned along the groove.